These ideas of mine Percolate the mind Trickle down the spine Swarm the belly, swellin' to a blaze

Lyric Meaning

The ideas stem in her mind, pass through her brain and her spinal chord and reach her bowels, giving her trouble assimilating food. Fiona has become visibly skinny before and during the promotion of her album The Idler Wheel… and she blames the stress for her loss of weight.

There is a scientific explanation for this. Our brain is like a “station” from where all the “trains” depart. The trains are our conscious commands and our instinctive commands in the form of action potentials and they are responsible for both the conscious contractions of our “voluntary muscles”, responsible for our locomotion and the movements of our head, limbs, etc., and the contractions of our “involuntary muscles”, responsible for our visceral functions, like digestion. Our mental health can affect our physiological bodily functions through a branch of our nervous system called autonomic nervous system.

The last line continues the butterflies metaphor, indicating that the innocuous butterflies that originated in her brain, once they’ve reached and infested the intestine, become aggressive and painful, causing her guts to burn.